These classes are application-dependent and directly affect on the capacity of the watermarking scheme. ![]() ![]() Extraction process of watermark may be dependent or independent of the original image or embedded watermark, which is based on level of required information that are classified into non-blind, semi-blind, or blind detection process. In this way, the watermark is less visible and more robust to some image-processing operations and attacks. Then, the coefficients are inverse-transformed to form the watermarked image. In these techniques, the watermark is embedded in the transform coefficients of the image. These techniques include discrete cosine transform (DCT), discrete Fourier transform (DFT), radon transform, discrete wavelet transform (DWT), etc. The watermarking procedure in which the techniques first transform an image into a set of frequency-domain coefficients is frequency-domain techniques. There exists a reverse relation between capacity, robustness, and imperceptibility and making a developed compromise between these conflict parameters is the core motivation of the most watermarking schemes. The peak signal-to-noise ratio (PSNR) is criteria that are used to evaluate imperceptibility. To be used as a means of copyright protection, the two main requirements of high robustness and capacity and high imperceptibility (low visibility) should be ensured for watermarking schemes. Digital watermarking is embedding hidden data into the multimedia in such a manner that it cannot be removed and its detection to verify the ownership of digital products. The protection of the digital data is an important topic to the owners of the multimedia products. With the fast growth of the Internet, people have paid more and more attention to the security of the network information.
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